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Search Results: 1 - 10 of 13229 matches for " Eric Hoberg "
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A Facile and Inexpensive Synthesis of 6-Ethynylbipyridine  [PDF]
Jianqiang Huo, John O. Hoberg
International Journal of Organic Chemistry (IJOC) , 2011, DOI: 10.4236/ijoc.2011.12006
Abstract: An inexpensive synthesis of 6-ethynylbipyridine has been accomplished using Sonogashira coupling of 2-bromo-6-iodopyridine with 2-methyl-3-butyn-2-ol. Subsequent Stille coupling with 2-(trimethylstannanyl) pyridine and hydrolysis provided the target compound in an overall high yield.
A Review of Hypothesized Determinants Associated with Bighorn Sheep (Ovis canadensis) Die-Offs
David S. Miller,Eric Hoberg,Glen Weiser,Keith Aune,Mark Atkinson,Cleon Kimberling
Veterinary Medicine International , 2012, DOI: 10.1155/2012/796527
Abstract: Multiple determinants have been hypothesized to cause or favor disease outbreaks among free-ranging bighorn sheep (Ovis canadensis) populations. This paper considered direct and indirect causes of mortality, as well as potential interactions among proposed environmental, host, and agent determinants of disease. A clear, invariant relationship between a single agent and field outbreaks has not yet been documented, in part due to methodological limitations and practical challenges associated with developing rigorous study designs. Therefore, although there is a need to develop predictive models for outbreaks and validated mitigation strategies, uncertainty remains as to whether outbreaks are due to endemic or recently introduced agents. Consequently, absence of established and universal explanations for outbreaks contributes to conflict among wildlife and livestock stakeholders over land use and management practices. This example illustrates the challenge of developing comprehensive models for understanding and managing wildlife diseases in complex biological and sociological environments. 1. Introduction Effective management and conservation of wildlife populations can be undermined by multiple causes. These include decreased and altered habitat and other direct anthropogenic effects, climate change, competition and predation from nonnative wildlife and domestic species, demographic challenges associated with small populations, multiple, incompatible management objectives for sympatric species or their habitat, and exposure to native and exotic infectious agents [1–4]. The consequences and interactions of these variables are difficult to understand and predict, and may vary by circumstances. This uncertainty, particularly when it occurs in complex sociological environments where stakeholders have differing values and objectives, presents substantial challenges for decision makers. In such uncertain environments, the absence of data and differing values can result in polarized debate among stakeholders. It can also serve as an impediment to the acquisition of data that would contribute to effective management. Respiratory disease outbreaks in bighorn sheep (Ovis canadensis) illustrate the challenge of identifying and managing disease in valued wildlife populations, where stakeholder perceptions and values clash [5]. Bighorn sheep are highly valued for recreational, ecological, philosophical, spiritual, and other reasons [6]. Bighorns have experienced a population decline of two orders of magnitude subsequent to 19th century settlement of western North
Phylogeny, ecological fitting and lung flukes: helping solve the problem of emerging infectious diseases
Brooks, Daniel R.;McLennan, Deborah A.;León-Règagnon, Virginia;Hoberg, Eric;
Revista mexicana de biodiversidad , 2006,
Abstract: traditional wisdom, based on assumptions of species-specific coevolutionary interactions between hosts and parasites, suggests that pathogens with multi-host life cycles are unlikely to move with their definitive hosts because their transmission requirements are so specialized. ecological fitting provides a theory of diffuse coevolution, which allows introduced pathogens with complex life cycles to become established and spread rapidly into native hosts if the resource required at each stage of the life cycle is both phylogenetically conservative (distributed among numerous species) and geographically widespread. the external appearance of life cycle complexity does not, therefore, on its own, predict the potential for an organism to become an emerging infectious disease. we apply this concept to explain a potential enigma, the presence of a lung fluke, haematoloechus floedae, endemic to north american bullfrogs, in costa rican leopard frogs, even though there are no bullfrogs extant in the country today, and none ever occurred where the parasite has been discovered. we then discuss how the integration of ecological and life history information within a phylogenetic framework can help biologists move from attempts to manage emerging infectious disease outbreaks to the ability to predict and thus circumvent the outbreak in the first place.
Phylogeny, ecological fitting and lung flukes: helping solve the problem of emerging infectious diseases Filogenia, flexibilidad ecológica y digéneos de pulmones: ayudando a resolver la crisis de las enfermedaes infecciosas emergentes
Daniel R. Brooks,Deborah A. McLennan,Virginia León-Règagnon,Eric Hoberg
Revista mexicana de biodiversidad , 2006,
Abstract: Traditional wisdom, based on assumptions of species-specific coevolutionary interactions between hosts and parasites, suggests that pathogens with multi-host life cycles are unlikely to move with their definitive hosts because their transmission requirements are so specialized. Ecological fitting provides a theory of diffuse coevolution, which allows introduced pathogens with complex life cycles to become established and spread rapidly into native hosts if the resource required at each stage of the life cycle is both phylogenetically conservative (distributed among numerous species) and geographically widespread. The external appearance of life cycle complexity does not, therefore, on its own, predict the potential for an organism to become an emerging infectious disease. We apply this concept to explain a potential enigma, the presence of a lung fluke, Haematoloechus floedae, endemic to North American bullfrogs, in Costa Rican leopard frogs, even though there are no bullfrogs extant in the country today, and none ever occurred where the parasite has been discovered. We then discuss how the integration of ecological and life history information within a phylogenetic framework can help biologists move from attempts to manage emerging infectious disease outbreaks to the ability to predict and thus circumvent the outbreak in the first place. Con base en el supuesto de coevolución a nivel de especies de parásitos y hospederos, tradicionalmente se asume como poco probable que aquellos patógenos con ciclos de vida que involucran varios hospederos acompa en a su hospedero definitivo a un nuevo ambiente, por lo especializado de sus requerimientos de transmisión. El fenómeno de flexibilidad ecológica aporta una teoría de coevolución difusa, que permite a los patógenos con ciclos de vida complejos, que han sido introducidos, establecerse y dispersarse de una manera rápida en hospederos nativos, si el recurso requerido en cada etapa del ciclo de vida es filogenéticamente conservado (se distribuye en numerosas especies) y a la vez, tiene una distribución geográfica amplia. Por lo tanto, la complejidad de un ciclo de vida no predice, por sí misma, el potencial de un organismo para provocar una enfermedad infecciosa emergente. Aplicamos este concepto para explicar el caso particular de un digéneo del pulmón de anfibios, Haematoloechus floedae, endémico de ranas toro de Norteamérica, que fue recolectado en ranas leopardo de Costa Rica, aún cuando actualmente no existen ranas toro en ese país, y nunca existieron en la región en donde se encontró al parásito. Asimismo,
The Monogenean Which Lost Its Clamps
Jean-Lou Justine, Chahrazed Rahmouni, Delphine Gey, Charlotte Schoelinck, Eric P. Hoberg
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0079155
Abstract: Ectoparasites face a daily challenge: to remain attached to their hosts. Polyopisthocotylean monogeneans usually attach to the surface of fish gills using highly specialized structures, the sclerotized clamps. In the original description of the protomicrocotylid species Lethacotyle fijiensis, described 60 years ago, the clamps were considered to be absent but few specimens were available and this observation was later questioned. In addition, genera within the family Protomicrocotylidae have either clamps of the “gastrocotylid” or the “microcotylid” types; this puzzled systematists because these clamp types are characteristic of distinct, major groups. Discovery of another, new, species of the genus Lethacotyle, has allowed us to explore the nature of the attachment structures in protomicrocotylids. Lethacotyle vera n. sp. is described from the gills of the carangid Caranx papuensis off New Caledonia. It is distinguished from Lethacotyle fijiensis, the only other species of the genus, by the length of the male copulatory spines. Sequences of 28S rDNA were used to build a tree, in which Lethacotyle vera grouped with other protomicrocotylids. The identity of the host fish was confirmed with COI barcodes. We observed that protomicrocotylids have specialized structures associated with their attachment organ, such as lateral flaps and transverse striations, which are not known in other monogeneans. We thus hypothesized that the clamps in protomicrocotylids were sequentially lost during evolution, coinciding with the development of other attachment structures. To test the hypothesis, we calculated the surfaces of clamps and body in 120 species of gastrocotylinean monogeneans, based on published descriptions. The ratio of clamp surface: body surface was the lowest in protomicrocotylids. We conclude that clamps in protomicrocotylids are vestigial organs, and that occurrence of “gastrocotylid” and simpler “microcotylid” clamps within the same family are steps in an evolutionary sequence, leading to the absence of these attributes in species of Lethacotyle.
A Logarithmic Additive Integrality Gap for Bin Packing
Rebecca Hoberg,Thomas Rothvoss
Computer Science , 2015,
Abstract: For bin packing, the input consists of $n$ items with sizes $s_1,...,s_n \in [0,1]$ which have to be assigned to a minimum number of bins of size 1. Recently, the second author gave an LP-based polynomial time algorithm that employed techniques from discrepancy theory to find a solution using at most $OPT + O(\log OPT \cdot \log \log OPT)$ bins. In this paper, we present an approximation algorithm that has an additive gap of only $O(\log OPT)$ bins, which matches certain combinatorial lower bounds. Any further improvement would have to use more algebraic structure. Our improvement is based on a combination of discrepancy theory techniques and a novel 2-stage packing: first we pack items into containers; then we pack containers into bins of size 1. Apart from being more effective, we believe our algorithm is much cleaner than the one of Rothvoss.
Current-driven transformations of the intermediate state patterns in type-I superconductors
J. R. Hoberg,R. Prozorov
Physics , 2008, DOI: 10.1103/PhysRevB.78.104511
Abstract: Dynamic structure of the intermediate state was studied in pinning-free thick Pb strips using real-time magneto-optical visualization. It is found that topological hysteresis can be lifted by applying sufficiently large current. Namely, laminar structure that appears on flux exit in a static case is turned into tubular when the sufficiently large transport current is present. Size and distribution of the flux tubes in static and dynamic regimes are different. Temperature, magnetic field and current phase diagram is discussed.
Dynamic Formation of Metastable Intermediate State Patterns in Type-I Superconductors
R. Prozorov,J. R. Hoberg
Physics , 2008, DOI: 10.1088/1742-6596/150/5/052217
Abstract: Structure of the intermediate state in type-I superconducting lead (Pb) is shown to be very sensitive to the ramp rate of an applied magnetic field. The configurations of resulting static patterns depend sensitively on the shape of the specimen. In particular, geometric barrier, present in the samples with rectangular cross-section, plays an important role in determining the sharp boundary between the phases of different topology. We propose that seemingly laminar (stripe) pattern obtained as a result of the fast field ramp is simply an imprint left behind by the fast-moving flux tubes. Our results confirm that flux tube phase is topologically favorable.
Población inmigrante y espacio urbano: Indicadores de segregación y pautas de localización
Martori,Joan Carles; Hoberg,Karen; Surinach,Jordi;
EURE (Santiago) , 2006, DOI: 10.4067/S0250-71612006000300004
Abstract: given the importance of immigrant population growth in spain, it would be interesting to study its distribution throughout the urban area. the field of statistics suggests different indicators that have a long tradition and permit the quantification of segregation of minority population groups. through the application of these tools in the metropolitan region of barcelona, this paper demonstrates the utility of analyzing segregation patterns within a city and detecting local patterns of this phenomenon. a new perspective of segregation can be obtained with the use of indicators designed for spatial statistics. the combination of these measures represents a useful procedure for the analysis of the distribution of the immigrant population in urban areas and its extension to different areas such as sociology, economics, urban studies, and housing policy
The Gravitino-Stau Scenario after Catalyzed BBN
Kersten, Joern;Schmidt-Hoberg, Kai
High Energy Physics - Phenomenology , 2007, DOI: 10.1088/1475-7516/2008/01/011
Abstract: We consider the impact of Catalyzed Big Bang Nucleosynthesis on theories with a gravitino LSP and a charged slepton NLSP. In models where the gravitino to gaugino mass ratio is bounded from below, such as gaugino-mediated SUSY breaking, we derive a lower bound on the gaugino mass parameter m_1/2. As a concrete example, we determine the parameter space of gaugino mediation that is compatible with all cosmological constraints.
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